Vertically adjustable safety table for near-counter-balanced supporting of instruments



March 28, 1961 P. c. JOHNSON 77,

VERTICALLY ADJUSTABLE SAFETY TABLE FOR NEAR-COUNTER-BALANCED SUPPORTING OF INSTRUMENTS Filed March 3, 1958 2 Sheets-Sheet 1 104 33 1 I l /j A34 FIG].

FIGI. j T M A I W ll 25' INVENTOR.

. 5 7 126 q 5 19 2 25 PHILIP C.JOHNSON ATTORNEYS March 28, 1961 P. c. JOHNSON VERTICALLY ADJUSTABLE SAFETY TABLE FOR NEAR-COUNTER-BALANCED SUPPORTING OF INSTRUMENTS 2 Sheets-Sheet 2 Filed March 3, 1958 FIGZ.

INVENTOR. PHILIP C. JOHNSON BY: W 9% ATTORNEYS wanna.

United States Patent 'ice. g: m M 28,196,

VERTICALLY ADJUSTABLE SAFETY TABLE FOR NEAR-COUNTER-BALANCED SUPPORTING F INSTRUMENTS Philip c. Johnson, Cincinnati, Ohio, assignor to F. and F. Koenigkramer Company, Cincinnati, Ohio, a corporation of Ohio Filed Mn. s, 1958, se No. 718,720

' 7 cl nns. retort-s9 invention relates to counterbalanced, adjustable height tables, and more particularly to tables for supporting heavy instruments, and the like.

' a hand appliedsmall forceof substantiallyconstantmag? An object of this invention'is to provide a table which will serve as a firm, solid support for instruments such as those which may be used by physicians making an eye examination. 7

Another object of this invention is to provide a table of the foregoing character which may be easily adjusted to any height within predetermined limits while a heavy instrument is supported thereon.

. Another object of this invention is to provide a table of the above character having means which tend to counterbalance the weight of an instrument supported whereby adjustment of the table to elevate or lower the instrument may be conveniently eifected by small forces of nearly constant magnitude applied by hand.

A further object of this invention is to provide a device of the above character which, vthrough counterbalancing of at least a substantial portion of theforces tending to effect lowering of the instrument protects the instrument supported, against damage from shocks resulting from violent changes in elevation.

A further object of this invention is to provide a device of the above character having brake means biased to set and preclude movement, particularly downward movement, of the instrument and supporting portion except in response to action by the-user.

A further object of this invention is to provide counterbalancing means, at least a portion of which constantly applies forces tending to counterbalance these forces applied by those parts of the device which may be raised and lowered, and a substantial portion of those forces applied by a useful load such as an instrument or the like supported thereon, and which alsocomprises auxiliary counterbalancing means which are operative'within predetermined limits of vertical adjustment, only one of which limits is coincident with a limit of the total rangeof vertical adjustment. V

Another object of this invention is to provide a device of the foregoing character, having means adapted to scoping leg, at spring-biased, parallelogram linkagezbias ing said leg toward extended condition, means. intercom; necting the telescoping portions of said leg to preclude:

separation thereof, auxiliary biasing means :operative through a, portion of the range of adjustment which does not include the portion'adjacent and including th e posia tion of maximum elevation or extension and means. J

nitude, will counterbalance the weight of the vertically adjustable portions and loads supported thereon whereby slight alteration of the, magnitude of theshand applied force permits positive, rapid, adjustment of elevation of the instrument supported with the exertion of very little efiort by the operator, 1 4 g A further object of this invention is to provide a device of the above character having brakemeans which serve to index the elevatable portion ofv the instrument support with reference to the non-elevatable portion thereof whereby azimuth rotation of the instrument inci-' dent to adjustment of its elevation is eliminated by setting of the brake. p l

The above and other features and objects of this invention will in part be obvious, and will in part be apparent to those having ordinary skill in the art to which this invention pertains, from. the following description an accompanying drawings, in which: v I

Fig. 1 is a view in side elevation of an instrument supporting table embodying this-invention, parts thereof being broken 'away and parts being shown in section,- to more clearly show details of construction andrelationship of parts when the table is extended to full or maximum height; a I I j a Fig. 2 is a view in side elevation of the table illus trated inFig. 1, portions thereofbeing broken" away to more clearly illustrate details of construction and showthe relationship of parts of the structure when the table is retracted to lowest or minimum height;

Fig. 3 is a fragmentary view in end elevation of .a table in a condition corresponding to that shown in Fig.- 2, portions thereof being omitted and other portions being broken away to more clearly illustrate a the details of construction; .g: I

Fig. 4 is a fragmentary "view in horizontal section; partly broken away and taken along the line IV-IV in Fig. 3 illustrating co-operation of portions of. lock or brake means and telescoping post structure;

Fig. 5 is a fragmentary view in vertical section, partly broken away taken; along the line V-V in Fig. 4;

Fig. 6 is a fragmentary view in horizontal section taken along the line VI-V I in Fig. 2;v

force plotted against table elevation} Fig. 8 isv a fragmentary view in section taken I the lineIX-JXinFig. 1;. p I I; Fig. 10'is a fragmentary viewinsection taken along the line X-.-X in Fig; 5; and

-Fig. 11 is a fragmentary viewirise'ctien takenalol'rig;

the line XI'-XI in Fig. 2.

An instrument table embodyin'g this invention is illus; tratedin the drawings. The tablehas a, unitary 2Q; which in top plan view is generally cruciform.I,.That is,; it has a centrallportion connecting four integral radially 22 in the drawings. =The foot21, is epI'eSentative of of the vfeet in that it has aglide lfl secured i rrfnxeg l r ela tion thereto and adapted to rest upon a supporting surface extending legor foot portions exemplifiedbyfeet 21* Fig. 7 is a graphic representation of such as a floor. Foot 22 has a glide 23 coupled to glide adjusting screw 24. The glide adjusting screw 24 is in threaded cooperative engagement with foot 22. Rotation of glide adjusting screw 24 serves to advance it axially to increase or decrease the degree of projection of adjustable glide 23 relative to the under side 25 of foot 22. Base 20 is thus. adapted to rest firmly upon a supporting surface with three fixedly related glides 19 serving to determine a reference plane relative to which glide 23 may be adjusted through rotation of glide-adjusting screw 24 to place glide 23 in base-supporting relation to the floor or other supporting surface to preclude rocking or other movement of base 20. Glide 23 may be adjusted, that is, advanced or retracted relative to foot 22 through rotation of glide-adjusting screw 24 in order to effect substantially equal distribution of the supported load among the glides 19 and 23.

A right cylindrical column 26 may be fabricated from a suitable metal bar, such as a steel bar. A column base 27 may be provided as an integral part of column 26, or, as shown in the drawings, be separately fabricated and then secured in fixed, co-operating relation to that column. Base '27 may have a bore extending therethrough in perpendicular relation to the bottom face 28 thereof and into which bore a portion of column 26 may be snugly pressed in order that under face 28 of column support 27 extends in radial relation to the axis of column 26. Auxiliary interlocking means, such as set screw 49 in engagement with threads 40 provided in column support 27 (Fig. 11), may be provided to preclude separation of column 26 from column support 27. Column 26 and column support 27 may be secured in fixed relation to base 20 by means such as screw bolts 23, as shown in Figs. 1 and 2. As shown, the heads of bolts 29 may engage a portion of base 20 when the threaded shanks of'the bolts 29 extend through an aperture provided in base 20 into threaded engagement with column support 27. Bolts 29, when drawn up tightly, secure face 28 of column support 27 in firm, abutting engagement with a horizontal co-operating face provided on base 20. Thus column 26 is firmly supported in a stationary upright position in fixed relation to and by base 20 and column support 27. A table top '30'has a bracket 31 secured to its under side by means such as screws 32. Bracket 31 has a recess provided therein, the axis of which extends perpendicularly to the upper surface 33 of table top 30. The upper portion of lift tube 34 is snugly received in the recess provided in bracket 31, for example, in a press fit. Thus tube 34 is firmly secured in fixed, co-operating relation with bracket 31 and a set or locking screw 35 may be provided to preclude relative movement of tube 34 and bracket 31' as shown in'Fig. 1. Tube 34 has a longitudinal,cylindrical bore adapted to telescopingly receive a portion of column 26. A compression spring 36 may be placed in the bore of lift tube 34 ahead of column 26 which is then inserted behind it. Lift tube 34 has a longitudinal fiat exterior face portion 37 disposed in perpendicular relation to a radius thereof. Face 37 extends from adjacent lower end 38 of lift tube 34 to a point substantially midway of the length of tube 34. A straight, elongate, longitudinally oriented slot 39 having closed ends, is provided inthe wall of lift tube 34. The longitudinally extending center line of slot 39 coincides with the center line of fiat face 37. One end of slot 39 is adjacent but spaced from end 38 of tube 34 while the other end of the slot 39 is disposed adjacent the longitudinal mid-point of lift tube '34 and also adjacent the upper end of flat face 37, nearest to bracket 31. Shoulder bolt 41 has a threaded portion 42 adapted to be received in cooperative threaded engagement with the threads provided in the wall of radially oriented recess 43 provided in column 26. A right cylindrical shoulder portion 44 of greater diameter than-threaded portion 42 extends from adjacent threaded portion 42 to adjacent the head of shoulder bolt Shoulder bolt 41 is advanced into recess 43 until the radially extending face of shoulder portion 44 adjacent threaded portion 42 is in firm abutting engagement with the external surface of column 26. A retaining plug 45 of nylon or the like extends diametrally through portion 42 and co-operates with the wall of recess 43 to retain bolt 41 in fixed relation to column 26. Shoulder portion 44 thus extends outwardly from the surface of column 26 through slot 39 in fixed radial relation to column 26. Shoulder portion 44 of shoulder bolt 41 is of a diameter slightly smaller than the width of slot 39 to allow free reciprocation of tube 34 relative to column 26, as shown most clearly in Fig. 4. Shoulder bolt 41 thus precludes any substantial rotation of lift tube 32 relative to column 26 and limits the primary relative movement of tube 34 to reciprocation longitudinally of column 26, the magnitude of such longitudinal reciprocation being substantially equal to one-half the length of lift tube 34.

Spring 36 is disposed in lift tube 34 between face 46 of bracket 31 and end face 47 of column 26. When table top 30 is in a position of full or maximum height relative to base 20 (Fig. 1), one end of spring 36 rests upon the upper end face 47 of column 26, while the upper end 48 of spring 36 is in spaced relation to face 46 of bracket 31. Spring 36 is of such length that it may be compressed from the unloaded condition in which it is shown in Fig. l to a condition in which its coils are in or nearly in contact, as shown in Fig. 2, as to effect an overall reduction in the spacing of spring end 48 from the spring supporting upper end face 47 of column 26 by a distance equal to substantially one-half themagnitude of the limited longitudinal reciprocation of lift tube 34 relative to column 26 as determined by shoulder bolt 41 inco-operation with column 26 and tube 34.

As shown in Figs. 3, 4, and 5, I provide a pair of coaxial oppositely extending radially oriented studs 50, 51 secured in fixed relation to tube 34 in any suitable manner such as by welds 52, 53. As shownmost clearly in Fig. 4, the axes of studs 50, 51 and lift tube 34 lie in a common plane substantially perpendicular to the common plane of the axes of shoulder bolt 41 and column 26 which latter axis coincides with the axis of lift tube 34.

A primary counterbalancing means is connected to studs 50, 51 which are secured in unitary relation to lift tube 34,. as previously explained, and by cap screws 55, 56 to column support 27. The primary counterbalancing means comprises duplicate short link bars 57, 58, 59, 60, 61, 62, 63, angle link bar 64, duplicate long links bars 65, 66, 67, 68, 69, 70, 71, 72, duplicate pivot pins 73, 74, 75, 76, 77, 78, and duplicate linkage pins 79, 80,81, 82. The portions of the spring biased linkage disposed to the left of tube 34 in Fig. 3, is substantially the same as the portion to the right of tube 34 in Fig. 3, except that link 62 is straight while link 64 is L-shape as shown in Figs. 1 and 2. Link 64 is so shaped to avoid interference between it and pedal 113. Each short link bar 57, 58, 59, 60, 61, 62, 63, has two apertures, one adjacent each end of the bar. Bars 57, 58 are adapted to pivot about the axis of stud 50. As shown in Figs. 3 and 4, a bushing 83 may be interposed between stud 58, tube 34 and links 57, 58. Portion 84 of bushing 83 serves to space link bars 57, 58 from lift tube 34 and a portion 85 of smaller; diameter serves as a bearing sleeve interposed between bars 57, 58 and stud 50, as shown indetail in Fig. 10. A spacing washer 86 may be interposed between links 57, 58, and annu-' l arly of portion 85, as thereshown. A lock washer, such as split lock washer 87, and nut 88 complete the assemblage to retain members 57, 86, 58 and 83 in relationto stud 50 and lift tube 34. Links 59 and 60, stud.

surface of pin 73 between split retaining rings 89,90, portions of which are received in respective grooves provided in pin 73. A spacing washer 86 is interposed between the adjacent faces of links 67 and68. Short link 58 and long link 65 are connected in similar manner by pivot pin 76. As shown in Figs. 1, 2, 3 and 8, long links 65 and 68 are pivotally joined by alinkage pin 79 which extends through apertures provided in the middle of the respective links 65, 68. Linkage pin 79 serves to couple links 65 and 68 for scissors-like action. Split retaining rings 91, 92 may be provided in co-operative engagement with grooves providedinpin 79, so as to preclude withdrawal of that pin from 'co-operative engagementwith bars 65, 68. As' shown, a spacing washer 86 may be provided annularlyxof pin 79between the bars 65, 68. Linkagepin 80couples links 66 and 67 in a similar manner, while linkage pins 81, and 82, respectively, couple links 69, 72, and 70, 71 in that same way. As shown most clearly in- Fig. 3, the linkage pins each serve. to couple only two respective link bars, while the pivot pins 73, 74, 75, 76, and 78, each serve to'couple four bars in spaced pairs. Short bars 62, 63 are in respective pivotal co-operation withpivot pins 75 and '78 and are in pivotally connected relation in co-operation with a bearing sleeve annularly of and supported by cap screw 56. v

As shown in Fig. 11, cap screw 56 extends through lock washer 95 and bearing sleeve 96 into threaded en-' gagement with column support 27. Links 61 and 64 pivotally engage the exterior surface of bearing sleeve 96 between column support 21-and washer 95 and are held in spaced relation by spacing washer 86.

-In similar manner, short link 62 and angle link 63 are supported in pivotal co-operation with a bearing sleeve, by cap screw 56.

As shown in Figs. 1, 2 and more particularly in Figs; 3 and 9, tension springs 97, 98, .99, 100, 101, 102, are provided extending between and in co-operation with respective pairs of pivot pins. .Thus, tension spring 97 extends between pivot pins 73 and 76 and a similar cor: responding spring 98 is in co-operating relation with the right hand ends of those springs as they are shown in Fig. '3. As shown in Fig. 9, a groove 103'isprovided annularly of pivot pin 73 adjacent the endthereof outboard of the portion of pin 73 co-operatively engaged by links 57 and 68. Tension spring 97 has a ring-like hook portion 94 which is partially received in groove 103 and co-operates with pivot pin'73 in a manner such that separation of the spring from the pivot pin is substantially precluded.- The length oftension spring 97,,when not under load, is less than the minimum spacing-of pivot pins 73 and-76 so that'when the hook-end portions 94 of tension spring 97 are in respective engagement with,

pivot pins 73 and 76, tension spring 97 isunder at least a minimum predetermined tension load at all times. Springs 97, 98 being of substantially the same length,

and being coupled to corresponding ends" of pair of pivot Thus the six springs 97, 98,99, 100,191, 102 being con-i. tinuouslyloaded in tension, resiliently bias the. link bar in which' tabletop 30 is at maximum elevation and the tension springs 97,99 and 101, as well as the springs disposed behind them, namely, tension springs 98, 100, 102, are under minimum tension loads. In the other limit position of tube 34, relative to column 26, tube end 38 is adjacent column support 27 (Fig. 2) when the upper end of slot 39 adjacent studs 50, 51 is resting against shoulder 44-0f shoulder bolt 41 (Fig. 5). In Fig. 2, the tension springs 97, 99, and 101, as wellvas springs 98, 100, 102, are subjected to maximum elongatioh and thus to maximum tension load.

The lifting force exerted by the counterbalancing means upon tube 34 and tending to urge it away from column support 27 is indicated in Fig. 7 which is a graphic representation of increasing elevation from left to right in units such as inches, for example, and of increasing force from bottom to-top in unit such as pounds. The solid line extending trom P through I to P, represents the efiect of the primary, continuously acting counterbalancing linkage. Thetension springs 97, 98, 99, 100, 101, '102' are thus adapted for use when an instrument 104 together with those-parts of the structure-Which are elevatable, have a total weight of approximately 7 80 pounds; as represented by the upper horizontal line in Fig: 7. Thus, at point P which corresponds to the position in which the upper end fiace'of slot 39 is in contact with shoulder 44 of shoulder bolt 41, as shown in Fig.5, the primary counterbalancing means provides a counterbalancing force of approximately 61 pounds.

When table 30 has been raised approximately 5 /2 inches,

an elevation corresponding to point I, the primary counterbalancing means provides an upwardly directed force of approximately 77 pounds. At an elevation of approxi mately 7 inches, the maximum upwardly directed force is provided by the primary counterbalancing means and of a magnitude of the order of 79 pounds, while in the position of maximum elevation in" which the parts are in a relation corresponding tothat shown in Fig. 5, the upwardly directed or counterbalancing force provided by the'primarycounterbalancing means is of the order of 74pounds. I v 1 V V U As previously explained, compression spring 36 is disposed between upper end face 47 of co lurnn'26 and face 46 of bracket 31. When table top 30 is in the position of maximum elevation, the upperend 48 of compression spring 36 is spaced from face 46 of bracket 31, a posit-ion corresponding to point P in the graph Fig. 7. Asta'ble' I spring 36' As table top30 is moved farther in thedown ward direction, compression spring 36 provides secondary counterbalancing force which is complementary to 1 the torce provided'by the "primary counterbalancing means and represented by the line P IP The area P ICP in the graph, Fig. 7, represents the coun terbalancing force contributed by compression spring 36 which varies fromjzero-force at pointI (5% inch eleva structure toward maximum elongation. 4 Since the-ends: v

of the linkage are respectively anchored to column sup; port 27 by cap screws 55, 5 6 andto lift tube 34 by studs 50, 51,.longitudinal telescoping movement oftube 34 relative to column '26, is directlyrelated to thecqndie, tion o n e. l g n BT 1 qu 1i.';b 1t4 whichserves to limit telescoping}reciprocationofiatube;

34'relative to column. 26 t9 -a j distance equalto :the} length of-slot'39 less the .diameter of shoulder *44; thereby: limits variation in linkage length onelohgationiotzi dis-* tauce i of equal magnitude. As" shown in Figitil, *t ube i34 is in a limit position-of maximum upward displacement tion) to approximately 13 pounds when table 30 has been moved to nunimum 'elevatiom with column '26, tube 1 34 andfshpulderbolt 41- in the relative positions shown in Fig- 5. Thus, the counterbalancing force provided by the counterbalancing means is represented by the line C-'-IP' This line indicatesthat points C and P, are minimum points corresponding to counterbalancingforces of approximately 74 pounds, whilethe maximum coon- ..'approximately '7 inches, is indicated by -the reference 1701 Y -approximately five pounds betw'een its minimum and character M. "The counterbalaiicing 'force *th'us 'varies 1 maximum liniit's; 11 The springs 36, .97,9s,199, 1100,' 101',-

l02f are fseletced to 'provide-a force of desired-'rnagnitude for' jjc'ounterba'lancingi'auseful load such 7 as a particular instrument resting-upon the table-top 30. Thus;

ing the total load to be counterbalanced is of the order of 76 pounds, the horizontal'line 54 in Fig. 7 represents the constant load and the vertical distance between line 54 and the line CI'M-P,, represents the unbalanced load corresponding to the respective position of vertical displacement of table top 30. Thus, vertical adjustment of the table top 30 of the illustrativeembodiment, would, as shown in Fig. 7, require'hand application of a supplemental force of the order of 2 to 3 pounds, depending upon the position of vertical'displacement of the table top 30 desired. If the useful load is changed, the total counterbalanced load is changed a like amount. To alter the counterbalancing force to a corresponding value, one pair of springs, 97-98, 99-100, or 101-102, may be removed, or removed and a pair of weaker or stronger ones substituted for those removed.

A brake or locking means is provided by means of which the unbalanced forces are utilized to more firmly secure lift tube 34 in fixed relation to column 26.

Brake block 105 is preferably a rectangular block having a bore adapted to co-operatively receive shoulder portion 44 of shoulder bolt 41 longitudinally along which block 105 is adapted to reciprocate between face 37 of tube 34 and the head of shoulder bolt 41 (Figs. 4 and Block 105 has a flat face 106 which extends in radial relation to shoulder 44 and is adapted to engage face 37 of lift tube 34 in flatwise face-to-face fashion. A generally U-shaped brake frame 107 is secured by brake block pins 108, 109 in pivotal relation to brake block 105. A brake shoe 110 is secured in pivotal relation to brake frame 107 by brake shoe pin 111, the axis of which extends in spaced, parallel relation to the aligned axes of brake block pins 108, 109, as shown in Figs. 4 and 5. Brake shoe pin 111 also extends through an aperture provided adjacent one end of brake rod 112 pivotally connecting the rod to brake frame 107. As shown most clearly in Figs. 6, 1, 3, and 2, a brake pedal 113 is mounted in rocking relation upon brake pedal bolt 1 14 between the head of bolt 114 and brake pedal spacing collar 115. Brake pedal bolt 114 extends into threaded engagement with and is supported by column support 27 and is locked in fixed relation thereto by look nut 116 (Fig.6). Brake pedal spacing collar 115 encircles the shank of bolt 114 between lock nut 116 and brake pedal 113. Brake pedal spring 117 has coils encircling brake pedal spacing collar 115." Arm 118 of spring 117 bears against a portion of base 20, while a second arm =1'19 bears against the under side of pedal 113. Spring 117 biases brake pedal 1'13 toward clockwise. rotation about bolt 114, asshown in Fig. '3. As shown, an angle lug 102 is pivotally secured to pedal 113 by any suitable means such as rivet 121. Lug 120, secured to pedal 1'13 by rivet 121, is free to swing about the axis of rivet 121. Lug 120 has an aperture through which a portion of brake rod 112 is adapted to extend, as shown particularly in Figs. 1, 2 and 6. Brake rod 1'12 is externally threaded adjacent lug 120 and in threaded co-operation with a pair of lock nuts 122, 123 disposed on opposite sides of lug 120. Lock nuts 122, 123, areadjustedlongitudinally by appropriate rotation so that. the efiective length of brake'rod 112 extending between brake pedal lug 120'and brake shoe pin 1 11 is such that when brake shoe 1'10 and break block 105 in the limit :position of its movement counterclockwise about bolt 114 in Fig. 3. Brake rod 112 connects pedal 113 .andbrake frameg107- which, as thus mechanically limited, cannot swing beyond a position -in.whichthe axis of pin 111 lies the plane perpendicular to the axis of colu'mrL-Z'? in which .place-Zthe-axisofpins.108,v

109.::1ies. Lock =nuts 122, 123, are: drawn:- up. in tight abutment with opposite-faces .of theinterposed -.por.tioni of lug .120 to lock lug 120 and brake rod 112 in 'substantially unitary relation. Spring 117 biases foot pedal 113'for' clockwise rotation, as shown in Fig. 3, and through brake rod 112 coupled to pedal 113 by lug 120', tends to rotate brake frame 107 in clockwise direction about the common axis of brake block pins 108, 109 as indicated by arrow 124 in Fig. 5. Such rotation'of brake frame 107 serves to tend to displace the axis of pins 108, 109andthe axis of pin 111 toward the common axisof column 26-and lift tube 34. That is to say, clockwise movement of brake. frame 107 about the axis of, pins 108, 109,; from the position'in which it is shown in Fig. 5, tends to reduce the radial spacing of the axis of pin 111 from the axis of column 26 and to reduce'the radial spacing of the axis of pins 108, 109 from the axisof column 26. Thus, spring 117 serves to bias the brake structure to move flat face106 of brake block 105 into abutment with fiat face 37 of lift tube 34 and to move substantially cylindrical face 125 of brake shoe 110 into conforming face-to-face abutment with an opposed portion of the exterior cylindrical face of lift tube 34 to grip lift tube 34 between brake block 105 and shoe 110, whenthe axis of brake shoe pin 111 is nearer to column support 27, than the axis of brake block pins 108, 109. Torsion spring 117 biases brake block 105 and brake shoe 110, of the brake or locking mechanism, to grip tube 34 so as to secure it against movement relative to column 26 in response to any band applied, upwardly directed force, the magnitude of which is less than a predetermined magnitude which is smaller than the magnitude of useful load counterbalancing force. Thus, upward and downward adjustment of top 30 and an instrument thereon, is easily effected when the brake or locking mechanism is released by actuation of pedal 113. However, if pedal 113 is not released, upward adjustment of top 30 requires application of much greater force, while attempted downwardadjustment merely serves to more firmly secure tube 34 in fixed relation to column 26 by setting the brake more tightly. As a result, top 30 firmly and steadily supports a counterbalanced load.

It may be noted that incident to setting, under biasing forces, of the brake o-r lock means, tube 34 is indexed by co-operative engagement of brake block face 106 with flat face 37 of tube 34. Thus, setting of the brake or lock means results in positive alignment of the tube 34 in a predetermined position of angular rotation while in any position of vertical adjustment. The sum of the load forces tending to move table top 30 and its associated lift tube 34 toward column support 27, preferably is as nearly equalled by the counterbalancing force applied to lift tube 34 by the spring biased linkage comprising primary counterbalancing lineans and the secondary or auxiliary counterbalancing means'comprising'resilient compression spring 36, as possible. Brake block 105, being secured by shoulder bolt 41 against axial displacement longitudinally of column 26, anchors one end of'brake frame 107 against movement longitudinally of column a 26. As explained above, spring 117 biases the lock tube 34 and shoe.110,'except when the brake-'or-locking means areirel'eased aszexplained below. As: previouslyexplained, .swinging of 2; brake; frame! 107 in l the direction: indicated by; arrow 124,; serves to. .apply forces tending:

to, advan e ak 1199K. e ti and br ke 1 9? F119. owa d;

9' the axis of column 26 to more firmly grip the interposed lift tube 34. Thus, the greater the uncounterbalanced force urging lift tube 34 downwardly, the more firmly tube 34 is gripped between brake shoe 110 and brake block 105. To permitlowering of table top 30, as desired, the brake or locking mechanism may be released by foot actuation of pedal 113. As shown particularly in Figs. 1 and 2, brake pedal 1 13 projects through a notch provided in base 20. The edge'126 definingthe bottom of the notch serves to limit swinging of brake pedal 113 in counterclockwise'direction,as shown in Fig. 3, and I prefer that the limit of such counterclockwise rotation correspond to a position in which the axis of brake shoe pin 11 1 will lie in a position between that in which it is shown in Fig. 5, and a position in which it coincides with a radial plane of column 26 in which the axis of brake block pins 108, 109, also lies.

It may be noted, as previously explained, that shoulder 44 of bolt 41 co-operates with the longitudinal edge faces bounding slot 39 to substantially preclude rotation of lift tube 34 relative to column 26. However, a small amount of rotation is possible as some pl-ayis normally present as free movement of tube 34 on column '26 is desired. Brake block :105 is urged into face-tmface engagement with flat face '37 which surroundsslot 39, when the :brake assembly is moved to set and lock lift tube 34 in fixed relation to column 26. The interaction of brake block 105 and flat face 37 incident to application of'the'brake; serves to index lift tube 34 even more closely. than; shoulder bolt 41 does, whereby-substantially. identicalorientation of lift tube 34in relation to'column "26: is? obtained when the brake is set to interlock thosemem bers against longitudinal displacement. Y

When the load tending to displace table top 30 downwardly toward column support 27 is decreased in magnitude to an extent that the force supplied by counterbalancing means tending to elevate the table top 30,,exceeds the'sum of the opposed downwardly acting forces and the force necessary to move tube 34 upwardly when the brake'is in spring 117 biased engagement therewith,

lift tube 34 tends to rise or move away from column sup-' port 27 and to carry with it brake shoe 110. Such movement of lift tube 34 tends to swing brake frame 107 in a direction opposite to that indicated by arrow 124, and the brake is thus automatically, partially released, allowing lift-tube 34 to move upwardly along column 26 away from column support 27 until thelower end of slot' 39 engages shoulder'bolt; 41. Thus, for example, when instruh1ent104 is lifted from table top30, table top 30 will follow instrument 104 upwardly until it reaches its maximum elevation as established by shoulder :screw 41. Thus, it is impossible fortabl'e 30 to remain in a lowered position from which it might be violently,spr'in g-propelled upwardly in responseto accidental trippingoffoot pedal 113. 'Ihe spring 117 biases the brake to set to adegree as will provide a drag which may be'overcomexby a counof approximately 18 to 100' percent. The particular springs used for a particular useful load are of course, selected to provide a useful load counterbalancing force gf a magnitude substantially equal to the useful load orce. v Each such combination of springs has a useful counterbalancing-force-curve corresponding to curve C-''I--M-'P of Fig. 7 and each such curve lies within a a small range of approximately six' pounds, like C-I-M-P,. Thus in using'the device, elevation adjusting forces of substantially similar magnitude need be supplied by the operator, whether a heavier or lighter useful load is supported by the device. v

A protective guard or housing 127 may be provided, as shown in Fig. 1, andsecured in fixed relation to base by screws 129 which co-operate with means such as lugs 128 in integral relation withbase 20. r e v Having described one preferred. embodiment of the invention, it will be apparent to those having ordinary skill in the art to which this invention pertains, that various modifications and changes may be made in the above described, illustrative embodiment without departing from the spirit or scope of this invention and the appended claims.

Therefore, what is claimed as new, and desired to be secured by Letters Patent is:

1. 'A support means comprising a base, a top, first and second telescoping members disposed between said base and top and in co-operating column-forming relation, said first telescoping member being secured to said base, said second telescoping member being secured to said top and being adapted to receive a portion of said first telescoping member, said second telescoping member being tubular and having a longitudinal flat face parallel to its axis, a longitudinal slot in said flat face parallel to the axis of said second'telescoping member, an interlocking member secured to said first'telescoping member and extending through said slot, a brake block mounted for reciprocation longitudinally of said interlockingmember, toward and away from saidlseoond telescoping member and adapted to co-operate with said flat face to index said second telescoping member to predetermined position of angular rotation relative to said first telescoping member, a brake frame pivotally secured to said brake block, a brake shoe pivotally securedto said brake frame and adapted'to engage a portionof-the exterior face of te'rbalancing force exceeding the opposed load by slightly less than the minimum useful load for which the device is.

designed. The counterbalancing' means thus also serves .should her-of equal astrength, but each pair need not be... equal to any other pair in strength. Infact', I have. found that'gfor' lighter weight instruments'onefjpa'ir of springs,

for g exar nple -101; 10 2',"rnay be timitt ed A setiof iten" am 1 n e to Hts? s vawayfrom saidba springs-comprising six of ftil1'-stjr'en'gth,lt wo of about threea1 ng h',m y

quarterrstrength and two of about onebeprovided for He illustrative; embodiment. By. us of a four;'or-.six.;pf these js'prings in'pair elation in. the pan.

within I ana ramimmerses;" ees; h we d I ceiinterbalanq ng intsamsuha V Q f? said second telescoping member, said-brakeframe being swingable and biased to advancesaidbrake. block and brake shoe into gripping relation ;to said second'telescopi'ng member in such manner that co-operation of gsaid brake shoe with said second telescoping member effects firmer gripping in response'tomovement of said second telescoping member toward said base, and meansfor swingingsaid brake frame to shift said brake shoe away from said second telescoping memberand said base to telescoping member toward said base, an elongate, par-.

allelogram linkage havingone of its endssecured in,pivot-, ally-fixed relation to'said base and the other of its ends,

secured in .pivotallyifixed,relation to said second,; teles'coping member, resilient means biasing saidgparal-lelo-g, gram-linkage toward extended, conditiom, whereby -s d,- secondtelescoping 'mer'nbe'r,-top, and a predetermined, useful load resting thereon, are urged away frorn ,sai d ,bas'eby forcesisubstantially;counterbalancinggthe force's, acting to advance theb'ase. -2.1A- devicein I u by; the fact that said resilient means' biasingsaid' paralle 'gramilinkage are tension spri'rigs yyhich bia v aid parallelo mber': I

the? secondtelescoping member toward;

accordance, with claim: 1 eharacte second I telescopin me M r re te? irectecl'w forces attributable.

' 'vieigh '1 er. structural 'partsfoffthejdevice adapted tojm'ove l 4 in therewith, i theforce essa yt o overcome 1 the predetermined drag of the brake means acting upon said second telescoping member whereby said second telescoping member will be advanced upwardly to its limit position remote from said base when the useful load'is reduced to a predetermined size.

3. Support means comprising a first elongate upright member, a second elongate member in telescoping relation to said first elongate member, an interlocking member secured in fixed relation to one of said elongate members'and extending into a longitudinal slot having closed ends provided in the other of said elongate members to preclude separation of said elongate members and limit longitudinal movement of the second member relative to the first elongate member, a resiliently biased parallelogram linkage being coupled adjacent one of its ends to said first elongate upright member and adjacent its other end to said second elongate member to resiliently bias said members toward extended relation, and indexing brake means anchored to one of said elongate members and adapted to clampingly grip the other of said elongate members, said brake means being adapted to index the second elongate member to a predetermined position of angular rotation relative to the first elongate member incident to setting of said brake, irrespective of the relative longitudinal displacement of said elongate members and said brake means being adapted to release the elongate member gripped thereby in response to relative movement of said elongate members toward extended relation.

4. Means-for counterbalancingly supporting a predetermined load for easy alteration of load elevation com prising a base, a top, first and second telescoping column-l forming members coupling said base and top, compressible resilient means adapted to co-operate with said telescoping column-forming members and resist telescoping relative movement thereof within a predetermined range of positions, brake means anchored to said first telescoping member and adapted to indexingly secure said second telescoping member against longitudinal movement relative to said first member and in a prededeterrnined position of angular rotation relative to said first member, means for releasing said brake means, said brake means being biased to predetermined set to offer a predetermined resistance to movement of said telescoping members toward extended column relation and to substantially preclude their relative movement toward telescoped relation, a parallelogram linkage having its opposite ends respectively anchored in fixed relation-to said first and second telescoping members, and resilient means biasing said linkage toward extended condition whereby said top is moved to maximum elevation when the load thereon is lessthan a predetermined portion of the predetermined load to be counterbalanced.

5. A support means comprising a first elongate memher, a second elongate member. in telescopic relation'to said first elongate'member, interlocking means interconnecting' said members to preclude separation of said elongate members and limit longitudinal movement of the second elongate member relative to the first elongate memher, a parallelogram'linkagecoupled adjacent one of its ends to'said first elongate member and adjacent its other,

end'to said second elongate member, spring means" extending crosswise of and-resilientlybiasing said parallelogramlinkagetoward extended relation, the baising force offsaid springmeans having a maximum-value when-the telescopic members are ata firstinter'media'te position spaced from the limits of relative movement and'de-J creasing as the elongate-membersfmove from said intera ,secpnd-iritermediate position adjacent 'Qand'more re- 1 tractedj than id,,first intermediatepbsition and: in further ptisrt onsftov supplement/the force" pt saidfirst. mentioned spring means,"said"scoi1d spring'm'eans' b'ias ingthe elongate members toward extended position, the second spring means being released when the members are in a further extended relation than said second intermediate position, whereby said members are continuously urged toward extended relation by substantially constant total force.

6. A device in accordance with claim 1 characterized by the fact that said interlocking means includes a brake block, that telescoping limiting means secured to said first elongate member and having a cylindrical portion thereof projecting outwardly through a slot in the second elongate member and through said brake block supported on said cylindrical portion for sliding movement toward and away from said second elongate member and for angular rotational movement about the axis of said cylindrical portion, that a U-shape brake frame straddles said second elongate member and is pivotally secured adjacent its ends to said brake block for pivotal movement about an axis perpendicular to the axis of said cylindrical portion, that a brake shoe adapted to cooperatingly engage said second elongate member is secured to said brake frame for pivoting about an axis parallel to the axis of brake frame pivoting, and that telescoping movement of said second elongate member in cooperation with said brake shoe pivots said brake frame to advance said brake shoe and brake block into firm interlocking engagement with said second elongate member and precluding further telescoping movement of said elongate members while remaining in cooperation with said second elongate member so as to release same in response to opposite movement of said second elongate member.

7. A device in accordance with claim 4 characterized by the fact that said interlocking means includes a brake block, that telescoping limiting meansare secured to said first elongate member and have a cylindrical portion thereof projecting outwardly through a slot inthe second elongate member and through said brake block supported on said cylindrical portion for sliding movement toward and away from said second elongate member and for angular rotational movement about the axis of said cylindrical portion, that a U-shape brake frame straddles said second elongate member and is pivotally secured adjacent its ends tosaid brake block for pivotal movement about an axis perpendicular to the axis of said cylindrical portion, that a brake shoe adapted to cooperatingly engage said second elongate member is secured to said brake frame for pivoting about an axis parallel to the axis of brake frame pivoting, that telescoping movement of said second elongate member in cooperation with said brake shoe pivots said brake frameto advance said brake shoe and brake block into firm interlocking engagement with said secondelongate member and precluding further telescoping movement of said elongate members'while remaining in cooperation with said second elongate member so as .to release same in response to opposite-movement of saidsecond elongate member, and that spring biased linkage urges said brake shoe toward locking engagement to'provid'e/ a predetermined resistance to movement of, said elongate members toward extendedirelation, said linkagebeing movable in bias overcoming direction to hold 'said brake shoe'andbrake block in released'relation to saidelong'ate members, whereby said elongate members amin -m a.

. UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No; 2 ,977 168 March 28 1961 Philip C. Johnson It is h'ereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 11 line 641., for baising' read biasing column 12 line 7 for the claim reference numeral 1" read 5 line 9, for means secured" read means are secured line 10, for "having" read have line 83, for the claim reference numeral "4" read 5 Signed and sealed this 29th day of August 1961.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents 

